KR101789325B1 - Method and apparatus for monitoring control channel in multiple carrier system - Google Patents

Abstract

A method and apparatus for monitoring a control channel in a multi-carrier system are provided. The terminal monitors the downlink control channel for a plurality of scheduled element carriers within the extended search space. The UE receives the downlink control information for the elementary carriers scheduled on the downlink control channel successfully decoded.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an apparatus and a method for monitoring a control channel in a multi-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to an apparatus and method for monitoring a control channel in a wireless communication system.

In a typical wireless communication system, although a bandwidth between an uplink and a downlink is set to be different from each other, only one carrier is mainly considered. The carrier is defined by the center frequency and the bandwidth. A multi-carrier system uses a plurality of component carriers (CCs) having bandwidths less than the entire bandwidth.

Multicarrier systems can support backward compatibility with existing systems and also have the advantage of greatly increasing the data rate through multicarrier.

LTE (Long Term Evolution) based on 3rd Generation Partnership Project (3GPP) TS (Technical Specification) Release 8 is a promising next generation mobile communication standard. The 3GPP LTE system is a single carrier system supporting only one bandwidth (ie, one CC) of {1.4, 3, 5, 10, 15, 20} MHz. However, LTE-Advanced (LTE-A) system, an evolution of 3GPP LTE, introduces multi-carrier.

In a single carrier system, control channels and data channels are designed based on a single carrier. However, it may be inefficient to use the channel structure of a single carrier system in a multi-carrier system.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for monitoring a control channel in a multi-carrier system.

It is another object of the present invention to provide a method and apparatus for transmitting a control channel in a multi-carrier system.

In an aspect, a method for monitoring a control channel in a multi-carrier system is provided. The method includes determining an extended search space in a control region in a subframe, monitoring a downlink control channel for a plurality of scheduled element carriers in the extended search space, and transmitting the downlink control channel on a successfully decoded downlink control channel And receiving downlink control information for the scheduled element carrier.

The size of the extended search space may be varied according to the number of downlink element carriers.

The size of the extended search space may vary according to the number of the plurality of scheduled element carriers.

The downlink control information may include a CIF (carrier indicator field) indicating the scheduled elementary carrier.

The extended search space includes a plurality of sub-search spaces corresponding to each of the plurality of scheduled element carriers, and the downlink control channel for each of the plurality of scheduled element carriers can be monitored in the corresponding sub-search space.

The plurality of sub search spaces may be continuous.

The plurality of sub search spaces may not be continuous.

The element carrier corresponding to the first sub search space among the plurality of sub search spaces may be a self-scheduling element carrier or an element carrier file having the lowest element carrier index.

In another aspect, a terminal is provided for monitoring a control channel in a multi-carrier system. The mobile station includes an RF unit for transmitting and receiving a radio signal, and a processor coupled to the RF unit, wherein the processor determines an extended search space in a control region within a subframe, And receives the downlink control information for the elementary carrier scheduled on the downlink control channel successfully decoded successfully.

A control channel for a plurality of element carriers can be scheduled in one subframe, thereby reducing a control channel blocking probability. In addition, decoding complexity can be reduced within the extended search space, burden on blind decoding of the control channel can be reduced, and battery consumption of the terminal can be reduced.

1 shows a structure of a radio frame in 3GPP LTE.
2 shows a structure of a DL subframe in 3GPP LTE.
3 is an exemplary diagram illustrating transmission of uplink data.
4 is an exemplary diagram illustrating reception of downlink data.
5 is a block diagram showing the configuration of the PDCCH.
6 shows an example of resource mapping of the PDCCH.
7 is an exemplary diagram showing monitoring of the PDCCH.
8 shows an example of a multi-carrier.
Figure 9 shows an example of cross-carrier scheduling.
10 shows an example of a CC set.
11 shows an example of the CIF setting.
12 shows another example of the CIF setting.
13 shows an extended search space including a plurality of sub search spaces.
14 shows an example of defining a sub search space based on CIF.
Fig. 15 shows an example of a change in CC order.
16 is a block diagram illustrating a wireless communication system in which an embodiment of the present invention is implemented.

A user equipment (UE) may be fixed or mobile and may be a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, a digital assistant, a wireless modem, a handheld device, and the like.

A base station generally refers to a fixed station that communicates with a terminal and may be referred to by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like.

Each base station provides communication services for a particular geographic area (commonly referred to as a cell). The cell may again be divided into multiple regions (referred to as sectors).

Hereinafter, downlink (DL) means communication from a base station to a terminal, and uplink (UL) means communication from a terminal to a base station. In the downlink, the transmitter may be part of the base station, and the receiver may be part of the terminal. In the uplink, the transmitter may be part of the terminal, and the receiver may be part of the base station.

1 shows a structure of a radio frame in 3GPP LTE. This can be referred to Section 6 of 3GPP TS 36.211 V8.5.0 (2008-12) "Evolved Universal Terrestrial Radio Access (E-UTRA), Physical Channels and Modulation (Release 8)". A radio frame is composed of 10 subframes indexed from 0 to 9, and one subframe is composed of two slots. The time taken for one subframe to be transmitted is referred to as a transmission time interval (TTI). For example, the length of one subframe may be 1 ms and the length of one slot may be 0.5 ms.

One slot may comprise a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain. OFDM symbols are used to represent one symbol period in the time domain since 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in the downlink. Limiting the multiple access scheme or name no. For example, an OFDM symbol may be referred to as another name such as a single carrier frequency division multiple access (SC-FDMA) symbol, a symbol period, or the like.

One slot exemplarily includes seven OFDM symbols, but the number of OFDM symbols included in one slot may be changed according to the length of a CP (Cyclic Prefix). According to 3GPP TS 36.211 V8.5.0 (2008-12), one subframe in a normal CP includes seven OFDM symbols, and one subframe in an extended CP includes six OFDM symbols.

The primary synchronization signal (PSS) is transmitted to the last OFDM symbol of the first slot (the first slot of the first subframe (index 0 subframe)) and the 11th slot (the sixth slot of the subframe index 5) do. The PSS is used to obtain OFDM symbol synchronization or slot synchronization and is associated with a physical cell identity. PSC (Primary Synchronization Code) is a sequence used in PSS, and 3GPP LTE has three PSCs. And transmits one of the three PSCs to the PSS according to the cell ID. The same PSC is used for the last OFDM symbol of the first slot and the 11th slot.

The Secondary Synchronization Signal (SSS) includes a first SSS and a second SSS. The first SSS and the second SSS are transmitted in an OFDM symbol adjacent to the OFDM symbol through which the PSS is transmitted. The SSS is used to obtain frame synchronization. The SSS is used to obtain the cell ID along with the PSS. The first SSS and the second SSS use different secondary synchronization codes (SSC). Assuming that the first SSS and the second SSS each include 31 subcarriers, two SSCs of length 31 are used for the first SSS and the second SSS, respectively.

The PBCH (Physical Broadcast Channel) is transmitted in four OFDM symbols preceding the second slot of the first subframe. The PBCH carries the system information necessary for the terminal to communicate with the base station, and the system information transmitted through the PBCH is called the master information block (MIB). In contrast, system information transmitted on a physical downlink shared channel (PDSCH) indicated by a physical downlink control channel (PDCCH) is referred to as a system information block (SIB).

As disclosed in 3GPP TS 36.211 V8.5.0 (2008-12), in LTE, a physical channel includes a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), and a physical downlink control channel (PDCCH) , Physical Control Format Indicator Channel (PCFICH), Physical Hybrid-ARQ Indicator Channel (PHICH), and Physical Uplink Control Channel (PUCCH).

2 shows a structure of a DL subframe in 3GPP LTE. A subframe is divided into a control region and a data region in a time domain. The control region includes a maximum of 3 OFDM symbols preceding the first slot in the subframe, but the number of OFDM symbols included in the control region may be changed. A PDCCH is allocated to the control region, and a PDSCH is allocated to the data region.

A resource block (RB) is a resource allocation unit and includes a plurality of subcarriers in one slot. For example, if one slot includes 7 OFDM symbols in the time domain and the resource block includes 12 subcarriers in the frequency domain, one resource block includes 7 × 12 resource elements (REs) .

The PCFICH transmitted in the first OFDM symbol of the subframe carries a control format indicator (CFI) regarding the number of OFDM symbols (i.e., the size of the control region) used for transmission of the control channels in the subframe. The UE first receives the CFI on the PCFICH, and then monitors the PDCCH.

The PHICH carries a positive-acknowledgment (ACK) / negative-acknowledgment (NACK) signal for a hybrid automatic repeat request (HARQ). The ACK / NACK signal for the uplink data transmitted by the UE is transmitted on the PHICH.

The control information transmitted through the PDCCH is referred to as downlink control information (DCI). The DCI includes a resource allocation (also called a downlink grant) of the PDSCH, a resource allocation (also called an uplink grant) of the PUSCH, a set of transmission power control commands for individual UEs in an arbitrary UE group, and / over Internet Protocol).

3 is an exemplary diagram illustrating transmission of uplink data. The UE monitors the PDCCH in the downlink subframe and receives the uplink resource allocation on the PDCCH 101. [ The UE transmits the uplink data packet on the PUSCH 102 based on the uplink resource allocation.

4 is an exemplary diagram illustrating reception of downlink data. The terminal receives the downlink data packet on the PDSCH 152 indicated by the PDCCH 151. [ The UE monitors the PDCCH in the downlink sub-frame and receives the downlink resource allocation on the PDCCH 151. [ The UE receives the downlink data packet on the PDSCH 152 indicated by the downlink resource allocation.

5 is a block diagram showing the configuration of the PDCCH. The base station determines the PDCCH format according to the DCI to be transmitted to the UE and attaches a cyclic redundancy check (CRC) to the DCI and identifies the radio network temporary identifier (RNTI) according to the owner or use of the PDCCH. To the CRC (510).

If the PDCCH is for a particular UE, the unique identifier of the UE, e.g., C-RNTI (Cell-RNTI), may be masked in the CRC. Alternatively, if the PDCCH is a PDCCH for a paging message, a paging indication identifier, e.g., P-RNTI (P-RNTI), may be masked on the CRC. If it is a PDCCH for system information, the system information identifier, system information-RNTI (SI-RNTI), can be masked in the CRC. A random access-RNTI (RA-RNTI) may be masked in the CRC to indicate a random access response that is a response to the transmission of the UE's random access preamble. A TPC-RNTI may be masked to the CRC to indicate a transmit power control (TPC) command for a plurality of terminals.

When the C-RNTI is used, the PDCCH carries control information (referred to as UE-specific control information) for the corresponding specific UE, and if another RNTI is used, the PDCCH is shared by all or a plurality of UEs and carries common control information.

The DCI to which the CRC is added is encoded to generate coded data (520). The encoding includes channel encoding and rate matching.

The encoded data is modulated to generate modulation symbols (530).

The modulation symbols are mapped to a physical RE (resource element) (540). Each modulation symbol is mapped to an RE.

6 shows an example of resource mapping of the PDCCH. This can be referred to Section 6.8 of 3GPP TS 36.211 V8.5.0 (2008-12). R0 denotes a reference signal of the first antenna, R1 denotes a reference signal of the second antenna, R2 denotes a reference signal of the third antenna, and R3 denotes a reference signal of the fourth antenna.

The control region in the subframe includes a plurality of control channel elements (CCEs). The CCE is a logical allocation unit used to provide the PDCCH with the coding rate according to the state of the radio channel, and corresponds to a plurality of resource element groups (REGs). A REG includes a plurality of resource elements. The format of the PDCCH and the number of bits of the possible PDCCH are determined according to the relationship between the number of CCEs and the coding rate provided by the CCEs.

One REG (represented by a quadruplet in the drawing) includes four REs, and one CCE includes nine REGs. {1, 2, 4, 8} CCEs can be used to construct one PDCCH, and each element of {1, 2, 4, 8} is called a CCE aggregation level.

A control channel composed of one or more CCEs performs REG interleaving and is mapped to a physical resource after a cyclic shift based on a cell ID is performed.

7 is an exemplary diagram showing monitoring of the PDCCH. This can be referred to section 9 of 3GPP TS 36.213 V8.5.0 (2008-12). In 3GPP LTE, blind decoding is used to detect PDCCH. Blind decoding is a method of checking whether a corresponding PDCCH is a control channel by checking a CRC error by demodulating a CRC of a received PDCCH (referred to as a PDCCH candidate) with a desired identifier. The UE does not know which CCE aggregation level or DCI format is used to transmit its PDCCH in the control area.

A plurality of PDCCHs can be transmitted in one subframe. The UE monitors a plurality of PDCCHs in every subframe. Here, monitoring refers to the UE attempting to decode the PDCCH according to the PDCCH format being monitored.

In 3GPP LTE, a search space is used to reduce the burden due to blind decoding. The search space is a monitoring set of the CCE for the PDCCH. The terminal monitors the PDCCH within the search space.

The search space is divided into a common search space and a UE-specific search space. The common search space is a space for searching a PDCCH having common control information, which is composed of 16 CCEs ranging from CCE indices 0 to 15, and supports a PDCCH having a CCE aggregation level of {4, 8}. However, a PDCCH (DCI format 0, 1A) carrying UE-specific information may also be transmitted to the common search space. The UE-specific search space supports PDCCHs with CCE aggregation levels of {1, 2, 4, 8}.

Table 1 below shows the number of PDCCH candidates monitored by the UE.

Search Space Type Aggregation level L Size
[in CCEs] Number of PDCCH candidates DCI formats UE-specific One 6 6 0, 1, 1A, 1B, 1D, 2, 2A 2 12 6 4 8 2 8 16 2 Common 4 16 4 0, 1A, 1C, 3 / 3A 8 16 2

The size of the search space is determined according to Table 1, and the start point of the search space is defined differently from the common search space and the UE-specific search space. Although the starting point of the common search space is fixed regardless of the subframe, the starting point of the UE-specific search space may be determined for each subframe according to the terminal identifier (e.g., C-RNTI), CCE aggregation level and / It can be different. When the starting point of the UE-specific search space is within the common search space, the UE-specific search space and the common search space may overlap.

The search space S ^(L) _k at the set level ^L {1, 2, 3, 4} is defined as a set of PDCCH candidates. The CCE corresponding to the PDCCH candidate m in the search space S ^(L) _k is given as follows.

Here, i = 0,1, ..., L-1, m = 0, ..., M ^(L) -1, N _{CCE , k} can be used for transmission of the PDCCH within the control region of sub- It is the total number of CCEs. The control region includes a set of CCEs numbered from 0 to N _{CCE, k} -1. M ^(L) is the number of PDCCH candidates at the CCE aggregation level L in a given search space. In the common search space, Y _k is set to 0 for two sets of levels, L = 4 and L = 8. In the UE-specific search space of the set level L, the variable Y _k is defined as follows.

Here, Y _-1 = n _RNTI ≠ 0, A = 39827, D = 65537, k = floor (n _s / 2), and n _s is a slot number in a radio frame.

When the UE monitors the PDCCH using the C-RNTI, the DCI format and the search space to be monitored are determined according to the transmission mode of the PDSCH. The following table shows an example of PDCCH monitoring in which C-RNTI is set.

Transfer mode DCI format Search space The transmission mode of the PDSCH according to the PDCCH Mode 1 DCI Format 1A Public and terminal specific Single antenna port, port 0 DCI format 1 Terminal specific Single antenna port, port 0 Mode 2 DCI Format 1A Public and terminal specific Transmit diversity < RTI ID = 0.0 > DCI format 1 Terminal specific Transmit diversity Mode 3 DCI Format 1A Public and terminal specific Transmit diversity DCI Format 2A Terminal specific CDD (Cyclic Delay Diversity) or transmission diversity Mode 4 DCI Format 1A Public and terminal specific Transmit diversity DCI format 2 Terminal specific Closed-loop spatial multiplexing Mode 5 DCI Format 1A Public and terminal specific Transmit diversity DCI format 1D Terminal specific Multi-user Multiple Input Multiple Output (MU-MIMO) Mode 6 DCI Format 1A Public and terminal specific Transmit diversity DCI Format 1B Terminal specific Closed-loop spatial multiplexing Mode 7 DCI Format 1A Public and terminal specific If the number of PBCH transmission ports is 1, then a single antenna port, port 0, otherwise, DCI format 1 Terminal specific Single antenna port, port 5 Mode 8 DCI Format 1A Public and terminal specific If the number of PBCH transmission ports is 1, then a single antenna port, port 0, otherwise, DCI format 2B Terminal specific Dual layer transmission (port 7 or 8), or single antenna port, port 7 or 8

The use of the DCI format is divided into the following table.

DCI format Contents DCI format 0 Used for PUSCH scheduling DCI format 1 Used for scheduling of one PDSCH codeword DCI Format 1A Used for compact scheduling and random access procedure of one PDSCH codeword DCI Format 1B Used for simple scheduling of one PDSCH codeword with precoding information DCI format 1C Used for very compact scheduling of one PDSCH codeword DCI format 1D Used for simple scheduling of one PDSCH codeword with precoding and pwwer offset information DCI format 2 Used for PDSCH scheduling of UEs set in closed loop space multiplexing mode DCI Format 2A Used for PDSCH scheduling of UEs set to open-loop spatial multiplexing mode DCI format 3 Used to transmit TPC commands of PUCCH and PUSCH with 2-bit power adjustments DCI format 3A Used for transmission of TPC commands of PUCCH and PUSCH with 1 bit power adjustment

We now describe a multiple carrier system.

The 3GPP LTE system supports the case where the downlink bandwidth and the uplink bandwidth are set differently, but it assumes one component carrier (CC). This means that the 3GPP LTE supports only the case where the bandwidth of the downlink and the bandwidth of the uplink are the same or different in a situation where one CC is defined for the downlink and the uplink, respectively. For example, the 3GPP LTE system supports a maximum of 20 MHz and supports only one CC for the uplink and the downlink although the uplink bandwidth and the downlink bandwidth may be different.

Spectrum aggregation (also referred to as bandwidth aggregation, or carrier aggregation) supports multiple CCs. Spectral aggregation is introduced to support increased throughput, prevent cost increases due to the introduction of wideband radio frequency (RF) devices, and ensure compatibility with existing systems. For example, if five CCs are allocated as the granularity of a carrier unit having a bandwidth of 20 MHz, it can support a maximum bandwidth of 100 MHz.

Spectrum aggregation can be divided into contiguous spectral aggregation, where aggregation occurs between successive carriers in the frequency domain, and non-contiguous spectral aggregation, where aggregation occurs between discontinuous carriers. The number of CCs aggregated between the downlink and the uplink may be set differently. The case where the number of downlink CCs and the number of uplink CCs are the same is referred to as a symmetric aggregation, and the case where the number of downlink CCs is different is referred to as asymmetric aggregation.

The size (or bandwidth) of the CCs may be different. For example, assuming that five CCs are used for a 70 MHz band configuration, 5 MHz carrier (CC # 0) + 20 MHz carrier (CC # 1) + 20 MHz carrier (CC # + 5MHz carrier (CC # 4).

8 shows an example of a multi-carrier. There are three DL CCs and three UL CCs, but the number of DL CCs and UL CCs is not limited. In each DL CC, PDCCH and PDSCH are independently transmitted, and in each UL CC, PUCCH and PUSCH are independently transmitted.

Hereinafter, a multi-carrier system refers to a system that supports multi-carrier based on spectrum aggregation. In a multi-carrier system, adjacent spectral aggregation and / or non-adjacent spectral aggregation may be used, and either symmetric aggregation or asymmetric aggregation may be used.

In a multi-carrier system, the linkage between DL CC and UL CC can be defined. The linkage may be configured through EARFCN information included in the downlink system information and is configured using a fixed DL / UL Tx / Rx separation relationship. The linkage refers to the mapping relationship between the DL CC where the PDCCH carrying the UL grant is transmitted and the UL CC using the UL grant. Alternatively, the linkage may be a mapping relationship between a DL CC (or UL CC) to which data for HARQ is transmitted and a UL CC (or DL CC) to which an HARQ ACK / NACK signal is transmitted. The linkage information may be a part of an upper layer message or system information such as an RRC message, and the BS may inform the UE. The linkage between DL CC and UL CC may be fixed, but may change between cells / terminals.

A PDCCH with separate coding means that the PDCCH can carry control information such as resource allocation for a PDSCH / PUSCH for one carrier. That is, PDCCH, PDSCH, PDCCH, and PUSCH correspond to 1: 1, respectively. A jointly coded PDCCH means that one PDCCH can carry out resource allocation for PDSCH / PUSCH of a plurality of CCs. One PDCCH may be transmitted through one CC, or may be transmitted through a plurality of CCs.

Hereinafter, an example of the division coding based on the downlink channel PDCCH-PDSCH will be described for the sake of convenience, but it can be applied to the relationship of the PDCCH-PUSCH as it is.

In multi-carrier systems, CC scheduling is possible in two ways.

First, the PDCCH-PDSCH pair is transmitted in one CC. This CC is called a self-securing CC. Also, this means that the UL CC to which the PUSCH is transmitted becomes the CC linked to the DL CC to which the corresponding PDCCH is transmitted. That is, the PDCCH allocates a PDSCH resource on the same CC or assigns a PUSCH resource on a linked UL CC.

Second, the DL CC to which the PDSCH is transmitted or the UL CC to which the PUSCH is transmitted is determined regardless of the DL CC to which the PDCCH is transmitted. That is, the PDCCH and the PDSCH are transmitted in different DL CCs, or the PUSCH is transmitted in the DL CCs in which the PDCCHs are transmitted and the unlinked UL CCs. This is called cross-carrier scheduling. PDCCH is transmitted on a PDCCH carrier, a monitoring carrier or a scheduling carrier, and a CC on which a PDSCH / PUSCH is transmitted is handled as a PDSCH / PUSCH carrier or a scheduled carrier.

The cross-carrier scheduling can be activated / deactivated on a UE-by-UE basis, and a UE with cross-carrier scheduling enabled can receive a DCI including a CIF. The UE can know which scheduled CC control information the PDCCH received from the CIF included in the DCI.

The DL-UL linkage predefined by cross-carrier scheduling may be overriding. That is, cross-carrier carrier scheduling can schedule a CC other than the linked CC regardless of the DL-UL linkage.

Figure 9 shows an example of cross-carrier scheduling. Assume that DL CC # 1 and UL CC # 1 are linked, DL CC # 2 and UL CC # 2 are linked, and DL CC # 3 and UL CC # 3 are linked.

The first PDCCH 701 of the DL CC # 1 carries the DCI for the PDSCH 702 of the same DL CC # 1. The second PDCCH 711 of the DL CC # 1 carries the DCI for the PDSCH 712 of the DL CC # 2. The third PDCCH 721 of the DL CC # 1 carries the DCI for the PUSCH 722 of the unlinked UL CC # 3.

For cross-carrier scheduling, the DCI of the PDCCH may include a carrier indicator field (CIF). The CIF indicates the DL CC or UL CC scheduled through the DCI. For example, the second PDCCH 711 may include a CIF pointing to DL CC # 2. The third PDCCH 721 may include a CIF indicating UL CC # 3.

Alternatively, the CIF of the third PDCCH 721 may be notified of the CIF value corresponding to the DL CC, not the CIF value corresponding to the UL CC. That is, the CIF of the third PDCCH 721 indicates the DL CC # 3 linked with the UL CC # 3, thereby indirectly indicating the UL CC # 3 on which the PUSCH is scheduled. Since the DCI of the PDCCH includes PUSCH scheduling and the CIF indicates DL CC, the UE can determine that it is the PUSCH scheduling on the UL CC linked with the DL CC. This has the effect of indicating a larger number of CCs than a method of informing all DL / UL CCs using a CIF having a limited bit length (e.g., 3-bit length CIF).

A UE using cross-carrier scheduling needs to monitor PDCCHs of a plurality of scheduled CCs for the same DCI format within the control area of one scheduling CC. For example, if the transmission modes of each of the plurality of DL CCs are different, each of the DL CCs may monitor a plurality of PDCCHs for different DCI formats. Even if the same transmission mode is used, if the bandwidths of the respective DL CCs are different, a plurality of PDCCHs can be monitored with different sizes of payloads of the DCI format under the same DCI format.

As a result, when cross-carrier scheduling is enabled, the UE needs to monitor PDCCHs for a plurality of DCIs in the control domain of the monitoring CC according to the CC-based transmission mode and / or bandwidth. Therefore, the configuration of the search space and PDCCH monitoring that can support it are needed.

First, in a multi-carrier system, the following terms are defined

UE DL CC set: A set of DL CCs scheduled to receive PDSCH by the UE

UE UL CC set: A set of UL CCs scheduled for the terminal to transmit PUSCH

PDCCH monitoring set: A set of at least one DL CC that performs PDCCH monitoring. The PDCCH monitoring set may be the same as the UE DL CC set or may be a subset of the UE DL CC set. The PDCCH monitoring set may include at least one of the DL CCs in the UE DL CC set. Or the PDCCH monitoring set may be defined independently of the UE DL CC set. The DL CC included in the PDCCH monitoring set can be set to always enable self-scheduling for the linked UL CC.

The UE DL CC set, the UE UL CC set and the PDCCH monitoring set may be set to be cell-specific or UE-specific.

10 shows an example of a CC set. (DL CC # 1, # 2, # 3, # 4) as the UE DL CC set, two UL CCs (UL CC # 1 and # 2) as the UE UL CC set, DL CC 2 (DL CC # 2, # 3) are allocated to the UE.

The DL CC # 2 in the PDCCH monitoring set transmits the PDCCH for the PDSCH of the DL CC # 1 / # 2 and the PDCCH for the PUSCH of the UL CC # 1 in the UE UL CC set in the UE DL CC set. The DL CC # 3 in the PDCCH monitoring set transmits the PDCCH for the PDSCH of the DL CC # 3 / # 4 and the PDCCH for the PUSCH of the UL CC # 2 in the UE UL CC set in the UE DL CC set.

The linkage can be established between the CCs included in the UE DL CC set, the UE UL CC set, and the PDCCH monitoring set. 10, a PDCCH-PDSCH linkage is established between a scheduling CC, a DL CC # 2 and a scheduled CC, and a DL CC # 2 and a UL CC # 1 are set to a PDCCH-PUSCH linkage. Also, a PDCCH-PDSCH linkage is established between the scheduling CC, DL CC # 3 and the scheduled CC, and a DL CC # 3 and a UL CC # 2 are set to the PDCCH-PUSCH linkage. The scheduling CC information or the PDCCH-PDSCH / PUSCH linkage information can be informed to the UE by the cell-specific signaling or the UE-specific signaling.

Alternatively, it may not link DL CC and UL CC for each of the DL CCs in the PDCCH monitoring set. After linking the DL CC in the PDCCH monitoring set and the DL CC in the UE DL CC set, the UL CC for the PUSCH transmission may be limited to the UL CC linked to the DL CC in the UE DL CC set.

The CIF may be set differently depending on the linkage of the UE DL CC set, the UE UL CC set, and the PDCCH monitoring set.

11 shows an example of the CIF setting. There are four DL CCs, indexed from 0 to 3 (i). There are also two UL CCs, indexed (j) of 0 and 1, respectively. The linkage of the UE DL CC set, the UE UL CC set, and the PDCCH monitoring set is the same as the example of FIG.

The first PDCCH 801 of the DL CC # 2 indicates the PDSCH 802 of the DL CC # 1. The CIF in the first PDCCH 801 is 0, indicating the index of the DL CC # 1.

The second PDCCH 811 of the DL CC # 2 indicates the PUSCH 812 of the UL CC # 1. CIF in the second PDCCH 811 is 0, indicating the index of the UL CC # 1. Setting the CIF value to 0 to indicate UL CC # 1 corresponds to a case where the DL CC and the UL CC have mutually independent CIF values. In addition, a flag field indicating whether the DCI received by the DCI is a downlink grant or an uplink grant may be included in the second PDCCH 811. Alternatively, the CIF in the second PDCCH 811 may point to DL CC linked to UL CC # 1. Here, since UL CC # 1 is linked with DL CC # 1 or DL CC # 2, CIF in the second PDCCH 811 indicates DL CC # 1 linked to UL CC # 1 with 0, And may point to DL CC # 2 linked to UL CC # 1. The UE can know that the second PDCCH 811 includes the uplink grant and is a PDCCH for UL CC # 1 or UL CC # 1 linked to DL CC # 2.

If the CIF is set to point to the UL CC and the linked DL CC, then the CIF does not need to point to the UL CC index and is always set to point to the DL CC index. It can be said that the index of the UL CC is determined according to the index of the linked DL CC. The UE can know whether the CIF indicates a DL CC or a DL CC linked with a UL CC according to whether the resource allocation in the PDCCH is a DL grant or an UL grant.

The first PDCCH 821 of the DL CC # 3 indicates the PDSCH 822 of the UL CC # 2. CIF in the first PDCCH 821 may be set to 1 to indicate the index of UL CC # 2 or to DL CC # 3 (or DL CC # 4).

The second PDCCH 831 of the DL CC # 3 indicates the PDSCH 832 of the DL CC # 4. The CIF in the first PDCCH 831 is 3, indicating the index of DL CC # 1.

12 shows another example of the CIF setting. There are five DL CCs, and the PDCCH monitoring set includes DL CC # 3 and DL CC # 4. Unlike the embodiment of FIG. 11, the CIF has a relative index value based on the monitoring CC to which the PDCCH is transmitted. That is, in the embodiment of FIG. 11, the CIF value is 0, 1, and 2 as the CIF values for DL CC # 1, # 2, # 3, and # 4 regardless of the monitoring CC and the PDCCH-PDSCH / PUSCH linkage to which the PDCCH is transmitted. And 3, respectively, the relative CIF value is given based on the monitoring CC.

The scheduled DL CCs linked to the DL CC # 3 are DL CC # 1, DL CC # 2 and DL CC # 3. 0, 1, and 2 are designated as indices for CIF in DL CC # 3, # 1, and # 2, respectively. The scheduled DL CCs linked to the DL CC # 4 are DL CC # 4 and DL CC # 5. Therefore, 0 and 1 are designated as indices for CIF in DL CC # 4 and # 5, respectively.

It is shown that each scheduling CC is allocated CIF in ascending order based on monitoring CC, but CIF can be allocated in descending order.

The first PDCCH 901 of the DL CC # 3 indicates the PDSCH 902 of the DL CC # 3. CIF in the first PDCCH 901 is zero. The second PDCCH 911 of the DL CC # 3 indicates the PDSCH 912 of the DL CC # 2. The CIF in the second PDCCH 911 is one. The third PDCCH 921 of the DL CC # 3 indicates the PDSCH 922 of the DL CC # 1. The CIF in the third PDCCH 921 is 2.

The first PDCCH 951 of the DL CC # 4 indicates the PDSCH 952 of the DL CC # 4. The CIF in PDCCH 951 is zero. The second PDCCH 961 of the DL CC # 4 indicates the PDSCH 962 of the DL CC # 5. The CIF in the second PDCCH 961 is one.

By setting the CIF value based on the monitoring CC, the CIF can indicate all DL CCs with a bit number less than the number of bits indicating the total number of DL CCs.

The method of independently allocating the CIF value for each PDCCH monitoring CC and DL-UL linkage has the advantage of pointing more CCs with a CIF having a limited bit length.

In order for the CIF to point to the UL CC for the PUSCH, it may be based on the monitoring CC. Alternatively, the UL CC may indirectly inform the DL CC linked by the CIF as indicated above.

An extended search space according to an embodiment of the present invention will now be described.

As shown in Table 1, in the 3GPP LTE system, the UE-specific search space defines 6 PDCCH candidates in each of the aggregation levels 1 and 2, and defines 2 PDCCH candidates in each of the aggregation levels 4 and 8. The common search space defines four PDCCH candidates at set level 4 and two PDCCH candidates at set level 8. This is based on a single carrier, where the CC to which the PDCCH-PDSCH is transmitted is the same.

In a multi-carrier system capable of cross-carrier scheduling, since a plurality of PDCCHs to be received by one terminal can be transmitted through one DL CC, the plurality of PDCCHs can not be scheduled only by the number of existing PDCCH candidates, . This is because the number of PDCCHs that can be transmitted to one DL CC is limited due to the number of PDCCH candidates even though a larger number of PDCCHs than the existing 3GPP LTE should be transmitted. Accordingly, the flexibility for scheduling a plurality of PDCCHs is low, and the PDCCH blocking probability can be increased. The PDCCH blocking probability refers to a probability that PDCCH scheduling can not be performed because a search space is duplicated between a plurality of UEs.

In addition, if there is a PDCCH-less CC without PDCCH for interference coordination in a multi-cell environment such as a heterogeneous network, a large number of PDCCHs can be concentrated in a specific DL CC have. It may be difficult to schedule a larger number of PDCCHs in the control region only by the size of the existing search space.

When cross-carrier scheduling is used in a multi-carrier system, an extended search space is proposed to extend the size of the insufficient search space.

If cross-carrier scheduling is used, a plurality of PDCCHs for one terminal can be transmitted in one DL CC. The number of PDCCH candidates may be increased at each aggregation level to increase the size of the search space in order to secure the terminal specific search space necessary for this. This is called an extended search space by comparing it with an existing search space.

Tables 4 and 5 below show examples of the increased search space.

Search Space Type Aggregation level L Size
[in CCEs] Number of PDCCH candidates UE-specific One 12 12 2 24 12 4 16 4 8 32 4

Search Space Type Aggregation level L Size
[in CCEs] Number of PDCCH candidates UE-specific One 10 10 2 20 10 4 12 3 8 24 3

In the above tables, the number of PDCCH candidates and the size of the search space are only examples.

The number of PDCCH candidates increased means that an increased search space is provided. The number of PDCCH candidates that are increased at each aggregation level may vary depending on the carrier aggregation capability, blind decoding capability, terminal category, and / or upper layer setting of each terminal.

The size of the search space may vary depending on the UE-specific signaling and / or carrier assignment information such as the RRC message. Alternatively, the size of the search space may be varied according to the number of DL CCs included in the UE DL CC set, the number of UL CCs included in the UE UL CC set, and DL-UL linkage. The size of the search space can be varied depending on whether the uplink grant and the downlink grant can be both transmitted or only one of them can be transmitted in a specific DL CC.

Let N be the number of DL CCs in the UE DL CC set, and M be the number of UL CCs in the UE UL CC set. N and M can inform the UE through RRC signaling.

Table 6 shows an example in which the size of the search space is variable.

Search Space Type Aggregation level L Size
[in CCEs] Number of PDCCH candidates UE-specific One 1 x 6 x C 6 x C 2 2 x 6 x C 6 x C 4 4 x 6 x C 2 x C 8 8 x 6 x C 2 x C

The C can be defined based on N and M. For example, C may be set to a larger value of N and M. As another example, C = N may be set when N is always M. As another example, C = N + M may be set. As another example, C may be determined depending on at least one of the carrier aggregation capability, the blind decoding capability, and the terminal category.

Table 7 shows an example in which the size of the search space is varied using arbitrary parameters i and j.

Search Space Type Aggregation level L Size
[in CCEs] Number of PDCCH candidates UE-specific One 1 x i x C i x C 2 2 x i x C i x C 4 4 × j × C j × C 8 8 x j x C j × C

The i, j may be determined depending on at least one of the carrier aggregation capability, the blind decoding capability, and the terminal category.

If there is a UE DL CC set and / or a UE UL CC set linked to the PDCCH monitoring set, the extended search space can be defined more efficiently based on the linkage.

Qm is the total number of CCs in the PDCCH monitoring set, Qd is the total number of CCs in the UE DL CC set, Qu is the total number of CCs in the UE UL CC set, and q is the CC index in the PDCCH monitoring set, q = 0, 1, ..., Qm-1.

Table 8 shows an example in which the size of the search space is varied using the parameter X.

Search Space Type Aggregation level L Size
[in CCEs] Number of PDCCH candidates UE-specific One 1 x 6 x X 6 × X 2 2 x 6 x X 6 × X 4 4 × 2 × X 2 × X 8 8 × 2 × X 2 × X

X = round (Qd / Qm), X = ceil (Qd / Qm) or X = floor (Qd / Qm). round (x) is a function that outputs an integer rounded to x. ceil (x) is a function that outputs the minimum value among integers greater than or equal to x. floor (x) is a function that outputs the maximum value among integers less than or equal to x.

Table 9 shows an example in which the size of the search space is varied using arbitrary parameters i and j.

Search Space Type Aggregation level L Size
[in CCEs] Number of PDCCH candidates UE-specific One 1 x i x X i x X 2 2 x i x X i x X 4 4 × j × X j × X 8 8 x j x j × X

The i, j are constants for defining an extended search space.

X can be defined for each monitoring CC in the PDCCH monitoring set. Let X of the monitoring CC with index q be Xq. And Xq may be the number of PDSCH CCs that can be scheduled in the q-th PDCCH CC. X in Tables 8 and 9 can be replaced by Xq. Xq can be expressed as the number of DL CCs linked to the monitoring CC having the index q or the number of UL CCs linked to the monitoring CC having the index q. For example, in the configuration of the CC set shown in FIG. 11, the monitoring CC is DL CC # 2, and DL CC # 3. Respectively to as q = 0, q = 1, the _{X 1 = 2, X 2 =} 2. In the configuration of the CC set shown in FIG. 12, the monitoring CC is DL CC # 3, and DL CC # 4. Respectively to as q = 0, q = 1, the _{X 1 = 3, X 2 =} 2.

Alternatively, Xq may be defined by a linkage with DL CC or UL CC that can be scheduled in the monitoring CC with index q. X ^d q is the number of DL CCs that can be scheduled in the monitoring CC with index q, and X ^u q is the number of UL CCs that can be scheduled in the monitoring CC with index q, Xq = X ^d q + X ^u q. < / RTI > Or Xq may be set to a larger value of X ^d q and X ^u q. In the configuration of the CC set shown in Fig. 11, X ^d ₀ = 2, X ^u ₀ = 1, X ^d ₁ = 2, and X ^u ₁ = 1.

The size of the extended search space can be adjusted according to the number of PDCCHs scheduled in the control region by adjusting the number of PDCCH candidates based on the parameter Xq for the monitoring CC.

The size of the extended search space can be expressed as C · M ^(L) · L. C is the number of scheduled CCs that can be scheduled in the PDCCH monitoring CC and M ^(L) is the number of PDCCH candidates in the CCE aggregation level L.

Now we describe how to divide search space by each CC within the extended search space.

The extended search space is a UE-specific search space, and its starting point can be defined in the same way as in the existing 3GPP LTE. Since the UE monitors a plurality of PDCCHs for a plurality of CCs in the extended search space, the search space can be divided for each CC in the extended search space. This is called a sub search space.

The sub search space is a search space for the UE to monitor the PDCCH for each CC within the extended search space. One sub search space may be defined for the DL CC and the UL CC linked to each other, and a different sub search space may be defined for the DL CC and the UL CC.

13 shows an extended search space including a plurality of sub search spaces. Assume that the extended search space starts at the CCE of index 4 among the CCE columns of the k-th subframe.

The extended search space includes a first sub search space, a second sub search space, and a third sub search space. N ₁ , N ₂ , and N ₃ are CCE indexes determined according to the size of each sub search space. Each sub search space is consecutive. Therefore, if the starting point of the first preceding sub search space (referred to as a reference sub search space) coincides with the start point of the extended search space, if the terminal knows the size of each sub search space, The starting points of the space can be known.

The starting point of the extended search space can be defined by equations (1) and (2) as in the existing 3GPP LTE. The starting point of the reference sub search space may be the same as the starting point of the extended search space.

The starting point of the extended search space and the number of sub search spaces are illustrative and not limitative. The extended search space may include a plurality of sub search spaces.

The base station can inform the terminal about the CC corresponding to each sub search space. However, this can lead to signaling overhead.

Therefore, the proposed method defines a corresponding sub search space according to a predetermined CC order. To this end, it is necessary to define a CC (referred to as CC) corresponding to the leading reference sub search space in the extended search space.

The reference CC may be the CC with the lowest CC index of the scheduled CC or the CC indicated by the lowest CIF. Alternatively, the reference CC may be a self-scheduling CC or a primary CC. The primary CC is a CC designated as a primary CC among a plurality of CCs, or a CC in which essential information is transmitted, and the CC knows that both the base station and the terminal are primary CCs.

After the reference sub search space for the reference CC is defined, a sub search space for the remaining CC can be sequentially defined based on the reference CC.

When a CC having the lowest CC index among the scheduled CCs is defined as a reference CC, a sub search space for each scheduled CC can be defined in ascending order of the CC indexes.

When the self-scheduling CC or the primary CC is defined as the reference CC, the sub search space for the CC having the lowest CC index among the remaining scheduled CCs is positioned next to the reference sub search space, A sub search space for the remaining scheduled CC can be defined.

The CC index may correspond to the CIF. As shown in FIG. 11, the CIF may correspond to a CC index in a UE DL CC set or a UE UL CC set. Alternatively, as shown in FIG. 12, the CIF may correspond to a relative index based on the monitoring CC to which the PDCCH is transmitted.

14 shows an example of defining a sub search space based on CIF. DL CC # 1 is the reference CC, and CIF = 0, so that it is allocated to the first search space. The CIF of the DL CC # 3 is 1, and thus is allocated to the second search space. The CIF of the DL CC # 2 is allocated to the third search space since it is the highest 2.

When defining the sub search space based on CIF, the CIF value mapped according to the CIF setting may be different for a specific CC. Therefore, it is possible to prevent the position of the sub search space for the specific CCs for the specific terminal from being continuously overlapped by changing the position of the sub search space for the various scheduled CCs allocated to one terminal according to the CIF have.

In the above example, the sub search space is allocated in the ascending order of the CCE index or the CIF, but the sub search space may be allocated in the descending order of the CCE index or the CIF.

The reference CC is not fixed, but may be changed periodically or according to a predetermined pattern by an instruction of the base station. Alternatively, the CC order allocated to the sub search space may be changed periodically or according to a predetermined pattern by an instruction of the base station. For example, after the sub search space is initially defined in ascending order of the CC indexes, the CC indexes are circularly shifted one by one in the next subframe.

Fig. 15 shows an example of a change in CC order. In the subframe n, a sub search space is defined in ascending order of CIF, with CC as CIF = 0 as a reference CC. In the next sub-frame n + p (p is an integer of 1), the CIF is cyclically shifted leftward one by one, and a sub search space is defined in the order of CIF = 2, 0,

Although the above embodiment shows continuous sub search spaces, the sub search spaces in the extended search space may not be continuous. That is, by defining an offset between sub search spaces, each sub search space can fall in an offset interval. For example, the second sub search space is defined in the CCE separated by the first offset from the first sub search space, and the third sub search space is defined in the CCE separated by the second offset from the second sub search space.

Although the communication between the base station and the terminal is described in the above embodiments, the technical idea of the present invention can be applied to the communication between the base station and the relay station, and / or the communication between the relay station and the terminal when there is a relay. If applied to communication in a relay period with a base station, the repeater can perform the function of the terminal. If applied to the communication between the repeater and the terminal, the repeater can perform the function of the base station. Unless otherwise specified, the terminal may be a terminal or a repeater.

16 is a block diagram illustrating a wireless communication system in which an embodiment of the present invention is implemented. Embodiments of the above-described extended search space can be implemented by the base station and the terminal.

The base station 2100 includes a processor 2101, a memory 2102, and a radio frequency unit 2103.

Processor 2101 implements the proposed functionality, process and / or method. In the above-described embodiment, the operation of the base station can be implemented by the processor 2101. [ The processor 2101 supports an operation for a multi-carrier and can set a downlink physical channel within the above-described determined search space.

Memory 2102 is coupled to processor 2101 to store protocols and parameters for multi-carrier operation. The RF unit 2103 is connected to the processor 2101 to transmit and / or receive a radio signal.

The terminal 2110 includes a processor 1211, a memory 1212, and an RF unit 1213.

The processor 2111 implements the proposed functions, procedures, and / or methods. In the above-described embodiment, the operation of the terminal can be implemented by the processor 2111. [ Processor 2111 may support multicarrier operation and monitor the PDCCH for multiple CCs within the extended search space.

Memory 2112 is coupled to processor 2111 to store protocols and parameters for multicarrier operation. The RF unit 2113 is connected to the processor 2111 to transmit and / or receive a radio signal.

Processors 2101 and 2111 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memories 2102 and 2112 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage media and / or other storage devices. The RF units 2103 and 2113 may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The module is stored in memories 2102 and 2112 and can be executed by processors 2101 and 2111. [ The memories 2102 and 2112 may be internal or external to the processors 2101 and 2111 and may be coupled to the processors 2111 and 2111 by various well known means.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (12)

CLAIMS 1. A method for monitoring a control channel in a multi-
If a received CIF is set, the UE monitors a plurality of UE-specific search spaces according to an aggregation level;
Monitoring downlink control channel candidates in the plurality of UE-specific search spaces; And
And receiving downlink control information on at least one downlink control channel successfully decoded from the downlink control channel candidates,
Wherein the plurality of UE-specific search spaces are in at least one specific element carrier among a plurality of downlink element carriers,
Wherein the plurality of UE-specific search spaces correspond to the plurality of downlink element carriers respectively indicated by the CIF, and the first UE specific search corresponding to the first downlink element carrier of the plurality of downlink element carriers, Space is composed of first downlink control channel candidates for the first downlink component carrier,
The number of downlink control channel candidates is changed according to the setting by the upper layer,
Wherein each of the plurality of UE-specific search spaces for monitoring the downlink control channel candidate is determined by each of the offsets. 2. The method of claim 1, wherein the size of the plurality of UE-
Wherein the number of downlink component carriers varies according to the number of the plurality of downlink component carriers. 2. The method of claim 1, wherein the size of the plurality of UE-
And the number of the downlink control channel candidates. The method according to claim 1,
Further comprising the step of receiving the CIF. delete 2. The method of claim 1, wherein the plurality of UE-specific search spaces are continuous. 2. The method of claim 1, wherein the plurality of UE-specific search spaces are discontinuous. The method of claim 1, wherein the plurality of UE-specific search spaces are located in the order of a carrier index. The method of claim 1, wherein the plurality of UE-specific search spaces are located in ascending order of a carrier index. The method of claim 1, wherein the plurality of UE-specific search spaces are located in descending order of a carrier index. A user equipment (UE) monitoring a control channel in a multi-cell environment,
A radio frequency (RF) unit for transmitting and receiving a radio signal;
And a processor coupled to the RF unit, the processor comprising:
Monitoring a plurality of UE-specific search spaces according to an aggregation level when a received carrier indicator field (CIF) is set;
Monitoring downlink control channel candidates in the plurality of UE-specific search spaces; And
Receiving downlink control information on at least one downlink control channel successfully decoded among the downlink control channel candidates,
Wherein the plurality of UE-specific search spaces are in at least one specific element carrier among a plurality of downlink element carriers,
Wherein the plurality of UE-specific search spaces correspond to the plurality of downlink element carriers respectively indicated by the CIF, and the first UE specific search corresponding to the first downlink element carrier of the plurality of downlink element carriers, Space is composed of first downlink control channel candidates for the first downlink component carrier,
The number of downlink control channel candidates is changed according to the setting by the upper layer,
Wherein each of the plurality of UE-specific search spaces for monitoring the downlink control channel candidate is determined by each of the offsets. delete

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